Abstract
The signs, symptoms, and amount of impairment expected at various concentrations of alcohol have been reported many times. Most of the other drugs do not produce characteristic signs and symptoms. The problem is further complicated when specimens contain combinations of alcohol and other drugs. There are a few reports of correlation's of concentrations of drugs with driving related tasks. The drugs in these studies included alcohol, benzodiazepines, marihuana, and barbiturates. Before people are charged with driving while impaired based on drug concentrations, research is needed concerning correlation's of drug concentrations and driving impairment not only for the above drugs alone and in combinations but also for other widely used drugs.